Morphometric measurements of the anterior skull base for endoscopic transoral and transnasal approaches

The objective of this study is to determine the bony limits of the transnasal and transoral approaches to the anterior skull base. The data we present are meant to assist surgeons in preoperative planning for lesions of the sella, clivus, foramen magnum, and odontoid. Using precise measurements undertaken on 41 high-resolution computed tomography scans from patients at the University of Pennsylvania without any history of sinus or sellar pathology, we sought to define the bony limits of transoral and transnasal approaches. Direct measurements and calculated angles were used to assess the dimensions of the anterior skull base. Using our measurements, a transnasal approach can reach an average of 22.5 mm below the plane of the hard palate to the body of C2, and a transoral route can reach 38 mm above the basion along the length of the clivus. Analysis of variance demonstrated no significant differences when subjects were grouped based on race or gender. The measurements outlined within this article help to define the relative dimensions necessary for adapted transoral and transnasal skull base surgeries.